Recording paper coated with microscopic capsules of coloring material, capsules and method of making



Jan. 9, 1962 N. MA ULAY 3,016,303

RECORDING PAPER COATED w MICROSCOPIC CAPSULES OF COLORING MATERIAL, CAPSULES AND METHOD 0 AK Flled Aug. 6, 1957 Sh s-Sheet 1 MAGNIFIED CROSS-SECTION 0F DISCRETE CAPSULE ACCORDING TO THE INVENTION FIG.2

I MAGNIFIED C SS-SECTION O CLUSTER OF DISCRET APSULES AC DING TO THE INVENTION Jan. 9, 1962 N. MACAULAY 3,016,308

RECORDING PAPER COATED WITH MICROSCOPIC CAPSULES OF COLORING MATERIAL. CAPSULES AND METHOD OF MAKING Flled Aug. 6, 1957 2 Sheets-Sheet 2 FIG.3

PHOTOMICROGRAPH MAGNIFIED L000 TIMES OF DISCRETE CAPSULES ACCORDING TO THE INVENTION FIG.4

PHOTOMICROGRAPH MAGNIFIED I,OOO TIMES OF DISCRETE CAPSULES ACCORDING TO THE INVENTION 1 ate rates This invention relates to a novel product comprising a substantially dry free-flowing powder of microscopic discrete capsules, to the process of producing said product, and to a pressure-sensitive record or copying material having a transfer coating of said microscopic discrete capsules on at least a portion of one surface thereof. The discrete capsules which make up the free-flowing powder of the invention possess a shell or wall containing therein a marking fluid.

Present pressure-sensitive copying systems are primarily of two types. One such system employs as a coating 2. mixture consisting of waxes, oils, carbon black and fillers which are applied to a sheet surface as a hot melt. This type of coating, which is typified by ordinary carbon paper, provides a mark under pressure by transfer at the areas of pressure of a complete mass of coating containing the carbon black or other pigment. This waxy mixture is relatively soft and of low tensile strength and is, therefore, not resistant to scufl or offset. The mark obtained on the copy sheet is also prone to smudge and offset onto bands and clothing.

A second type of pressure sensitive copying system employs, on one side of a sheet, a continuous coating containing marking fluid inclusions. This type of system illustrates previous efforts employing minute droplets of a marking fluid in a transfer coating to be used with record material, particularly with record material in manifold form. Typical of this type of product are the record or copying materials disclosed in British Patent 392,220 and US. Patents Nos. 2,374,862; 2,548,366 and 2,550,466. In accordance with these patents, the paper of the record material is coated on one surface with a continuous film containing minute droplets of an oily marking fluid. In this type of copying sheet, the marking fluid may be colored or it may be colorless but capable of forming a color by a chemical reaction with another chemical upon being brought into contact with each other. Under the pressure of writing or typing, the coating ruptures and the droplets of marking fluid exude on to the copy sheet to make a mark by direct coloration or color transfer or by forming a color by chemical reaction with a coreacting chemical on the adjacent surface of the copy sheet. The difliculty with products of this type is that the surface of the coated sheet is susceptible to scufling, abrasion and incidental rubbing which unavoidably causes rupture of the film, release of the marking fluid, and consequently smudge or offset or both. Also, on storage of the sheets, the coating material tends to dry out and crack, particularly when bended or folded, thus releasing the marking fluid through the resulting cracks to smudge oroffset an adjacent copy sheet or the hands or clothing. In the case of such coatings containing a colorless marking fluid, this difficulty arises only when the ruptured film is in contact with a copy sheet or other source of the coreacting chemical. But this is a very real disadvantage since such copying materials are not only used, but usually stored, in this condition.

Further work has been carried out in an attempt to overcome some of the objectionable features of the coatings employing fluid inclusions described hereinabove. An example of such work is described in Green Patentv No. 2,712,507. According to this patent a coating for pressure-sensitive copying materials is prepared in which the fluid inclusions of marking materials are produced having a wall about them which is somewhat more concentrated with respect to colloid solids than the remainder of the continuous dried coating on the surface of the paper. This product is predicated upon the theory that the walls about the fluid inclusions are tougher than the remainder of the colloid coating material, thus cracks which develop in the coating are said to be more prone to run between the fluid inclusions than through them and the leakage of marking fluid is said to be reduced. This type of coating requires that the walls of the fluid inclusions be of the same hydrophilic colloid material as the coating on the paper in which the fluid inclusions are dispersed, since the patent produces the fluid inclusions in the same aqueous system which is applied to paper and dried to form the continuous coating. This type of product suffers from several disadvantages. First of all, as stated above, it usually employs an aqueous coating system in which the hydrophilic colloid forming the walls about the fluid inclusions is the same as that of the continuous coating on the paper. This leads to lack of flexibility and versatility in control of the product and in coating operations. it requires that aqueous coating methods be employed. This is a serious disadvantage since aqueous coatings require that special grades of generally more expensive paper be employed and even then often results in buckling, distortion, warping of the paper since water tends to strike through or penetrate the paper. Additionally, aqueous coatings are generally not suitable for spot application or application to limited areas of one side of a sheet of paper. They are generally suitable only for application to the entire side of a sheet to produce a continuous coating.

The above disadvantages are particularly serious since in producing manifold business forms, the' coating of marking material is usually applied to the backs of the sheets of paper or web. Even when a colorless colorforming dye intermediate is employed as the marking material it is generally applied to the backs of the sheets so as to react with a coreactant or developing agent which is applied to the fronts of the sheets of a manifold when pressure is applied to the sheets. During the usual handling which such business forms must undergo in their assembly, cutting, perforation, etc., the coating on the backs of the sheets containing marking fluid is in contact with the fronts of the copy sheets, which may or may not have the developing agent. When the coating on the backs of the sheets is continuous, the passage of the sheets over mill rolls, punching of holes, perforation and guillotining of edges will produce smudging or oflset at areas of pressure. This undesirable smudging and offset can be minimized by spot coating the coating material on limited areas which are 'less subject to unavoidable mechanical pressure until actually used to produce copying.

It is an object of the present invention to provide a substantially dry free-flowing powder of microscopic discrete capsules of marking fluid which may be applied to paper and other web material to provide pressuresensitive materials which avoid the disadvantages of the prior art.

It is another object of this invention to provide a substantially dry free-flowing powder of microscopic discrete capsules of marking fluid which may be applied to paper in a variety of ways and which does not require an aqueous coating system in preparing a pressure-sensitive copying material from the capsules.

It is a further object of this invention to provide a process for producing the substantially dry free-flowing powder of microscopic discrete capsules having an outer shell of a material which is a non-ionizable water-soluble film-former or a hydrophobic water-insoluble film-former according to the invention.

It is an additional object of this invention to provide a superior pressure-sensitive copying or record material having the microscopic discrete capsules of marking fluid applied to at least a portion of one side of a sheet of paper or other web material.

It is also an object of this invention to provide a superior pressure-sensitive copying or record material having the microscopic discrete capsules of marking fluid applied to at least a portion of at least one side of a sheet of paper by means of a carrier or binder which is of a different material from that of the walls of the capsules.

The above enumerated objects, as well as other objects, together with the advantages of the invention, will be readily comprehended by persons skilled in the art upon reference to the following description, taken in conjunction with the annexed drawings.

In the drawings:

FIG. 1 is a greatly magnified cross-section of a discrete capsule making up the free-flowing powder according to the invention in which is the marking fluid and 11 is the wall of the capsule;

FIG. 2 is a greatly magnified cross-section of a cluster of discrete capsules which is frequently produced in accordance with this invention, in which the reference numerals have the same significance as in FIG. 1;

FIG. 3 is a photomicrograph magnified 1000 times of the discrete capsules of marking fluid making up the freeflowing powder of the invention; and

FIG. 4 is a photomicrograph magnified 1000 times of another sample of discrete capsules of marking fluid making up the free-flowing powder of the invention.

The free-flowing powder of microscopic discrete capsules of the invention containing a marking fluid comprises a capsule shell or film containing a marking fluid. In FIG. 1 of the drawings, the shell is indicated at 11 and the liquid inclusion of marking fluid is shown at 10. Frequently the discrete capsules are produced in the form of aggregates or clusters as shown in FIG. 2. While FIG. 2 illustrates a cluster of six discrete capsules, the number of capsules or spheres in a cluster is usually not so great. The shell or film of the capsules is of a nonpermeable nature and comprises a substance which is substantially insoluble in the liquid of the marking fluid. The capsule shell remains intact and retains the fluid within. Under substantial pressures, such as that of a pencil, pen or typewriter key, the shell will break and release the marking fluid which then marks or stains any receptive or copy material with which it comes in contact. The marking fluid may contain a colored substance which produces a direct transfer to a copy sheet or which may be an uncolored color-forming dye intermediate which reacts with a coreactant present on the copy sheet to produce a color transfer. When the microscopic discrete capsules of the invention are aflixed over at least a portion of a surface, such as a surface of a sheet of paper, the coated sheet then acts as a pressure-sensitive copying material at the coated area.

The size of the microscopic capsules is desirably such that they may be dispersed in any of the common media used as binders or coatings or other backing material for application to paper without producing a surface rough to the touch. These micro-capsules may be considered as being analogous to pigment particles and they can be dispersed in any binder/vehicle combination in a manner similar to ordinary pigments. Various binder systems may be employed such as aqueous binders, an organic solvent/binder system, a plastisol or organosol binder system, a hot melt coating system or an ink-type coating which may be set to the paper by absorption, oxidation, evaporation, heat or moisture.

The discrete microscopic capsules of the invention are desirably of from between. about 0.1 and 70 microns in diameter. More desirably, the diameter of the capsules is from about 0.5 to 20 microns. For preferred results, it has been found that a capsule diameter of between about 1 and 5 microns is most satisfactory. When the particle size exceeds 20 microns in diameter, a coating of the capsules on a paper surface may feel slightly rough to the touch. Below a diameter of one micron, the capsules are less sensitive to rupture when subjected to the pressure employed to produce copying through rupture of the capsule shell. Since it is desired to employ the microscopic capsules of the invention in pressure-sensitive copying systems which do not require the use of excessive pressures, it is desirable to provide capsules having a diameter of from about 1 to 5 microns. The microscopic capsules of the invention falling within the various particle size ranges described hereinabove exist as a free-flowing powder.

It has been found that one convenient shell thickness is approximately ,6 to A of the diameter of the capsules. When shell thicknesses substantially in excess of /3 of the diameter are produced, it has been found that the capsules are more diflicult to rupture and the ability to produce a copy is reduced. With shell thicknesses substantially less than of the diameter, it has been found that the capsules are more prone to rupture prematurely and thus smudge or offset in a normal handling and preparation of the paper product. As will be appreciated by those skilled in the art, the sensitivity to rupture under pressure is dependent upon the size of the capsule as well as the thickness of the wall, with the larger size capsules having greater tendency to rupture when subjected to pressure than the smaller size capsules. Generally speaking, it is desirable to employ as thin a capsule shell as is practical.

The microscopic capsules of the invention are produced by first providing a stable emulsion having as a continuous phase the film-former material which is capable of forming the shell of the capsule. The discontinuous phase of the emulsion shall constitute the marking fluid which comprises the pigment, colored dye or colorless color-forming dye intermediate suspended or dissolved in a non-volatile liquid. An essential characteristic of a film-forming substance is that it be substantially insoluble in the marking fluid. The emulsions are produced by placing the two mutually insoluble liquids in a blender or emulsifier and by agitation producing a stable emulsion with droplets of marking fluid of the desired particle size, preferably 1 to 5 microns in diameter. The resulting emulsion is then dried, preferably by spray drying, or the continuous film-forming material first condensed around the emulsified droplets by curing or other means and then spray dried. The resulting product is a dry free-flowing powder.

The discrete microscopic capsules may be prepared by several types of emulsification processes. For example, one process which produces microscopic capsules of approximately one micron diameter is as follows: About 20 parts by weight of a non-volatile liquid containing up to 25% by weight of a pigment, colored or colorless color-forming dye intermediate is emulsified into a solution containing from about 5 to 40 or 50 parts of a filmforming material by agitation in a high-speed blender. In other words, the liquid droplets shall preferably comprise between about 23% and by Weight of the capsules. When the particle size of the marking fluid is substantially uniform and of the desired diameter, the resulting emulsion is sprayed into a drying chamber or spray drier to evaporate the solvent of the film-forming material. Upon drying, the film-former produces a shell about the non-volatile marking fluid. The dry freeflowing powder so produced is collected by means of a cyclone chamber and, if necessary, washed with a solvent capable of removing any marking fluid which may exist on the shell of the capsule. After washing, the powder is air dried and stored ready for use.

Another capsule-forming process employing a hot melt procedure which might be employed is as follows: About 50 parts by weight of a non-volatile liquid containing up to about 25% by weight of a pigment, colored or colorless color-forming dye intermediate is emulsified into about 50 parts by weight of a molten 100% solids film-former composition. The emulsion is produced in a high-speed agitator as in the above procedure. When the particles of color-forming marking fluid are of satisfactory particles size, the resulting emulsion =is hot sprayed into a chilled chamber and the resulting solidified free-flowing powder of discrete microscopic capsules is collected.

A third process for producing the microscopic capsules in accordance with the invention employs plastisol or organosol sphere formation. The general procedure is as follows: Up to about 50 parts by weight of a nonvolatile liquid containing up to about 25% by weight of pigment or colored or colorless color-forming ,dye intermediate is emulsified into 50 parts by weight of a dispersion of a polymeric material in a plasticizer. The dispersion employed may contain up to about 30% of a volatile diluent. The emulsion is produced by a highspeed agitator, as in the foregoing procedures, and is sprayed into a hot air chamber or spray drier where the individual particles produced are heated to a temperature such that the resin-plasticizer, film-forming combination mutually dissolves and cures to provide a rigid shell around the marking fluid particles. This resulting powder is then collected.

The shell 11 of the microscopic capsules of the invention is produced from a film-former which may be organic or inorganic in nature, capable of providing interactive forces such as are capable of producing a network in the form of a continuous dry film or shell. The film-former must be substantially insoluble in the marking fluid employed, and when the shell is produced it must not permit permeation of the marking fluid. The shell formed may be hard and brittle or, if desired, made soft and flexible by the incorporation of a plasticizer. The film-forming materials may be either of the nonionizable Water-soluble type or the hydropholic waterinsoluble (organic solvent-soluble) type. Among the filmformers which may be employed to produce the shell of the capsules are the following: acrylate and methacrylate resins, such as polymethylmethacrylate and po-lyacrylic acid; alkyd resins, such as those produced from esters of ethylene glycol and terephthalic acid; animal glues; casein; cellulose derivatives, such as hydroethyl cellulose, carboxymethyl cellulose, methyl cellulose, cellulose acetate, cellulose acetate butyrate and nitrocellulose; a conmarone-indene resin; furan resins, such as those of furfuraldehyde and acetophenone', petroleum hydrocarbon polymer resins, such as the Piccopale resins; isobutylene resins, such as polyisobutylene; isocyanate resins, such as polymers of polyesters and tolylene diisocyanate; melamine resins, such as melamine-formaldehyde; phe' nolic resins, such as phenol-formaldehyde resins, etc.; polyamide resins, such as alkoxy substituted nylon; rubbers, both natural and synthetic, GR-S, etc.; shellac; styrene resins, such as polystyrene, styrene-divinyl-benzene and styrene-divinyl sulfide; terpene resins, such as polyterpene; urea resins, such as urea-formaldehyde resins and urea-acetaldehyde resins; vinyl resins, such as polyvinyl chloride and polyvinyl acetate; vinylidene resins, such as vinylidine chloride-vinyl chloride (Saran); natural and synthetic waxes, such as par-afi'in and candelilla wax; and zein. Additionally, inorganic filmformers, such as sodium silicate, may be employed, although this film-former is less desirable because it is more difficult to emulsify.

The film-formers may be used alone or in combinations, where compatible, or with various plasticizers and modifying agents which impart improved characteristics, such as flexibility, scuff resistance, solvent impermeability, or,

in the case of water soluble film-formers, agents which cause water impermeability to the film-former. As an example of the latter type of material, formaldehyde may be employed to harden the shell of the capsule produced from a water-soluble film-former. A plasticizer may be one of many types of materials which modify a particular film or shell to give suitable elasticity, flexibility and toughness, etc. Among some of the satisfactory plasticizers which may be employed are: adipic acid esters, such as dioctyl adipate and dibutyl adipate; biphenyl derivatives, such as chlorinated biphenyl; glycol derivatives, such as polyethylene glycol of molecular weight of 200 to 20,000, polypropylene glycols, ethylene glycol dibutyrate and ethyl phthalyl ethyl glycolate; hydrocarbons, such as the polyaromatic hydrocarbon oils; acid esters and ethers, such as butyl or isooctyl esters and glycol ethers of lauric, oleic, citric, abietic, adipic, azelaic, benzoic, palmitic, phosphoric acids, etc.; phthalic acid derivatives, such as dimethyl-, diethyl-, dibutyl-phthalates; polyesters, such as Flexol R2H of Carbide and Carbon Co.; sulphonic acid derivatives, such as n-ethyl-, 0-, p-toluene-sulphonamides; tall oil derivatives, such as the methyl esters of tall oil, etc.

The marking fluid may comprise any liquid, whether organic or inorganic which will provide a suspending or dissolving medium for the pigment, or colored or colorless color-forming dye intermediates. Desirably, the fluid medium within the capsule shell shall have a low volatility, i.e., wherein less than about 10% of the liquid evaporates through the shell wall over a period of several years of normal storage. Fluids having vapor pressure of less than 0.01 mm. of mercury at 25 C. are particularly satisfactory in this respect. Additionally, the fluid shall desirably have a low freezing point, i.e., a freezing point of less than 0 F., preferably as low as -30 F. Also, the fluid shall desirably have a high boiling point which will provide reduced volatility at temperatures of use. Fluids having boiling points in excess of 100 C. are usually suitable in this respect. An additional important property of the fluid is that it have a flash point above the temperature of proposed use. above 100 C. are generally satisfactory. As those skilled in the art will appreciate, the product will be more useful, permanent and safe with liquids having higher boiling points and flash points and lower volatility and freezing points. Of course, the fluid must not dissolve the filmformer or shell of the capsules. Among the satisfactory fluids which may be employed are those listed below in Table 1:

TABLE 1 V.P., mm. Freezing Boiling Flash Compound Hg. Point, Point. Point,

at 20 0. C. O. at 760 F.

mm. Hg.

100 Sec. mineral oil polyethylene glycol (mol.

wt. 400) 4-8 435 diethylene glycol. 0. 01 8. 0 245. 8 290 dipropylene glycol 0.01 231. 8 280 thiodiethylene glycol.-. 0. 0]. --l0. 0 282.0 320 pentanediol-1,5 0. 01 15. 6 242. 5 265 monoamylnaphthalene O. 01 279 255 dibutyl maleate 0. 01 280. 6 285 (ii (2-ethy1 hexyl) maleate 0. 01 -60 209 (10 365 mm. ethoxytriglycol 0. -18. 7 255. 8 275 dioctyl phthalate 1.3 (200 -46 231 (5 425 0.) mm.) chlorinated biphenyl (Arochlor 1248 Monsanto) 7 340 379 methyl phthalyl-ethyl glycollate 0. 01 35 189 (5mm) 374 dibutyl phthalata -35 340 338 cottonseed oil 582 rapeseed oil 10 530 As will be appreciated, the free-flowing powders in accordance with this invention permit extreme flexibility in the choice of film-formers and marking fluids.

The marking fluid may contain a colored pigment or Fluids having a flash point' dye or it may contain a colorless color-forming dye intermediate which will react with a coreactant when brought into contact with it to produce a colored finish. The line of demarcation between pigments and dyes is often difficult to delineate. As used herein, a pigment is considered to be a colored or color-forming substance which is insoluble in the fluid of the marking fluid. Examples of pigments which may be employed are: carbon blacks, iron blues, phthalocyanines, cadmium reds, ultramarine blues, phosphoand molybdotungstic acid laked colors. A dye or dye former is herein considered to be colored or colorforming compound soluble in the fluid of the marking fluid. Among the dyes and dye formers which may be employed are: triphenylmethane, e.g., malachite green and crystal violet, azo dyes, diazonium salts, indigoid dyes, phthalocyanine dyes, anthraquinone dyes, acridine dyes, azine dyes, oxazine dyes, thiazine dyes and thioindigoid dyes.

One type of colorless color-forming dye system which may be advantageously used in the products of the invention is that described in British Patent No. 757,136. In accordance with that patent a colorless color-forming dye intermediate, such as an ether of a triphenylmethane dye former is maintained in an alkaline condition by neutralizing the dye former with an alkaline substance, in which form the dye former is colorless, and then producing a color by bringing the alkaline colorless dyestutf into contact with an excess of an acid which converts the dye former into a colored product. Among the colorless ethers of triphenylmethane dyestuffs which may be employed are the butyl ethers of methyl violet 2B, methyl violet 10B, magenta, malachite green A. In accordance with one embodiment of the present invention the marking fluid of the microscopic capsules may contain the colorless color-forming dye intermediate along with a small amount of an alkaline substance such as sodium carbonate, potassium hydroxide, etc. These capsules are applied to one surface of sheets of paper. On the opposite side of some sheets of paper is placed suflicient acid which when brought into contact with marking fluid containing the colorless color-forming dye intermediate will neutralize the dye intermediate thereby producing a color. Among the acids which may be employed to coat the opposite surface of the sheets are tannic acid, gallic acid and stearic acid. Also one may employ an acidic clay such as attapulgite clay. As will be apparent to those skilled in the art from the teachings of this disclosure, it is possible to incorporate the acid into the marking fluid of the discrete capsules and to place the colorless colorforming dye intermediate on the opposite sides of the sheets of paper. In either instance when pressure is exerted through two or more sheets in a manifold, rupture of the capsules will produce intermixing of the reacting chemicals to produce a color or copy at the sites Where pressure is applied.

A coating of capsules and binder weighing 1 to 6 lbs., and preferably 2 lbs., per 500 sheets of 20"x 30" paper in which 50 to 95% of the weight of the coating consists of capsules has been found to be satisfactory.

Among the important advantages of the free-flowing capsule powders of the invention is the extreme flexibility and versatility in the manner in which they may be applied to web material, such as paper, to provide a pressure sensitive copying material having a coating of the rupturable capsules according to the invention which permits copying. What is also important is that the free-flowing capsule powders may be applied to a surface of a sheet of paper by means of a binder material which provides adhesion of the capsules to the paper surface, which binder is of a different material and different type of substance from that of the shells of the capsules. Also, binder coatings of various thickness may be employed, permitting precise control over the thickness of the coating on the paper. In essence the binder employed need serve only as an adhesive to hold the capsules to the paper. Only a small thin layer of binder is needed rather than a thick coating covering the capsules. Both aqueous binders and non-aqueous binders may be employed. Since non-aqueous binders may be used, it is not necessary to employ expensive papers thereby providing additional economies as well as a superior product. One of the particular advantages of the free-flowing powders of the invention is that it may be employed with a hot melt wax binder or dispersed in a printing ink vehicle. In the case of printing ink vehicles, the microscopic capsules may be dispersed in them and the resulting product reverse printed on a paper sheet at the same time as ordinary line printing is done. This is particularly satisfactory since it provides an excellent means of spot application whereby prescribed areas on the backs or fronts of the sheets of paper may be coated with capsules. This is one of the particular advantages of the present invention since it permits application of a transfer film or coating of capsules to only those areas of the paper where it is desired.

In order that the present invention may be better understood, the following examples of products prepared according to the invention are given for purposes of illustration. Although the number of film-formers, marking fluids, coloring and color-forming materials and binders is so great, and the number of combinations of materials suitable for making the capsules and record materials containing the capsules over an area thereof is vast, those skilled in the art will be able to readily practice the invention from reading the examples which illustrate the preparation of the products of the invention. Portions of components are given in terms of parts by weight, unless otherwise specified.

Example I This example describes the preparation of microscopic capsules prepared by spray drying an emulsion of mineral oil in aqueous hydroxyethylcellulose.

About 30 parts of second mineral oil containing 4.5 parts of Mogul A (Godfrey Cabot, Inc.) carbon black (high volatile contentlow oil absorption-336 Angstrom units mean diameter) was emulsified into 700 parts of a 10% aqueous solution of hydroxyethylcellulose (having a viscosity of 250-350 centipoises at 20 C. when in the form of a 5% aqueous solution). Emulsification was accomplished by agitating the 10% aqueous solution of hydroxyethylcellulose by itself in a Waring Blendor and then pouring in the oil solution slowly while agitation was continued. A fine particle size (one micron) stable emulsion was thus produced. The resulting emulsion was injected via a fine air feed nozzle into a heated spray drying chamber of a temperature of between about 225-265 F. and the dried product collected. On examination, microscopic capsules ranging from 1 to 10 microns were observed. The capsules exuded black oil when subjected to ordinary writing pressure.

Example II This example describes the preparation of microscopic capsules prepared by spray drying an emulsion of mineral oil in aqueous hydroxyethylcellulose.

About 17 parts of 100 second mineral oil containing 5% by weight of the butyl ether of malachite green A was emulsified into 3000 parts of a 5% aqueous solution of Cellosize WP-40 (hydroxyethylcellulose which when in the form of a 2% aqueous solution at 20 C. possesses a viscosity of 75 to centipoises). An emulsion was produced and then spray dried in accordance with the procedure of Example I. A free-flowing powder of microscopic capsules was obtained.

Example III This example describes the preparation of microscopic capsules containing a marking fluid containing a colorless color-forming dye intermediate.

About 4.5 parts of the butyl ether of methyl violet was dissolved in 180 parts of an equal part mixture of Arochlor 1254 (a chlorinated diphenyl having a Saybolt viscosity of 44-48 seconds at 210 F.), amyl diphenyl and amylnaphthalene. The resulting solution was colorless. This solution was emulsified into 600 parts of a 10% aqueous solution by hydroxyethylcellulose in accordance with the procedure of Example I and the resulting emulsion spray dried in accordance with Example I. A free-flowing powder of microscopic capsules having particle sizes from about 0.5 to 10 microns diameter was obtained.

When the capsules were subjected to pressure they exuded colorless marking fluid which produced a strong color when absorbed on a paper impregnated with a surface of attapulgite clay or a paper surface coated with tannic acid.

Example IV This example describes the preparation of microscopic capsules containing carbon black.

About 150 parts of a 10% Arochlor 1248 (a chlorinated diphenyl having a Saybolt viscosity of 36-37 seconds at 210 F.) and 90% 100 second mineral oil mixture containing 22.5 partsof carbon black was emulsified into 75 parts of an aqueous solution of water soluble urea-formaldehyde resin (Uformite 400-67% solids) and 2.5 parts of extra low viscosity (-25 centipoises in a 2% aqueous solution at 25 C.) carboxymethylcellulose in 175 parts of water. The emulsion was produced in accordance with the procedure of Example I and diluted with 600 parts of water, and while continuing the rapid agitation, sufiicient concentrated hydrochloric acid' was added to produce condensation and precipitation of the urea formaldehyde resin. The resulting mixture was agitated for another five minutes, filtered, and the filter cake washed with water and acetone and then agitated with toluene to remove any free oily liquid. The mixture was again filtered and the filter cake air dried and then subjected to further drying at 105 C. Under microscopic examination the resulting dry, free-flowing powder was found to consist of agglomerated microscopic capsules ranging in diameter from between about 4 to 50 microns. On applying pressure to these capsules, the Walls ruptured and black oil was exuded in copious quantities.

Example V This example describes the preparation of microscopic capsules prepared from an emulsion of mineral oil in cellulose acetate.

About 100 parts of 100 second mineral oil containing about 25% by weight of nigrosine dye was emulsified into a solution of 50 parts of cellulose acetate in 600 parts of acetone in accordance with the procedure of Example I. The resulting emulsion was sprayed through an aspirator into the air to evaporate the acetone and the resulting dry microscopic capsules collected. The capsules were of about 50 micron diameter particle size. When this free-flowing powder of capsules was subjected to writing pressure, the cellulose acetate shells of the capsules were ruptured and the oil containing the nigrosine exuded therefrom in copious quantities.

Example VI sules exuded the blue colored fluid when subjected; to pressure to give a blue mark on a receptive surface.

10 Example VII This example describes the preparation of capsules containing a colorless color-forming dye intermediate.

About 50 parts of second mineral oil containing about 2 parts of the butyl ether of malachite green A (Color Index No. 657) in the alkaline condition was emulsified into a solution of 40 parts of Zein and 1 part of sodium hydroxide in 200 parts of methanol. The emulsification was accomplished in accordance with the procedure of Example I. The resulting emulsion was spray dried by atomizing the emulsion into the air to provide rnicro-capsules ranging in size from about 1 to 60 microns. When the resulting capsules were coated' to a sheet of paper and the sheet of paper placed in contact with the surface of an adjacent sheet which was coated with tannic acid, and pressure applied to the sheets in the form of pencil writing, a strongly colored mark was produced on' the surface of the sheet containing the tannic acid.

Example VIII Microscopic capsules produced in accordance with Example III to the extent of 30 parts of free-flowing capsule powder was placed into 70 parts of a 5% solution of Du Pont isobutyl methacrylate in benzene. The resulting dispersion was applied to the backs of sheets of bond paper with a doctor blade and then subsequently air dried. The fronts of these sheets of paper had been sensitized with attapulgite clay. When a manifold of sheets were stacked one above the other, with the capsule coated surfaces adjacent to the clay sensitized surfaces and writing pressure applied, a copy was produced on the fronts sensitized with clay at the sites where pressure was applied.

Example IX Microscopic capsules produced in accordance with Example VII were placed in a flexographic vehicle (Bensing Bros. and Deeney D-536) (a water soluble protein dissolved in water) to the extent of 30 parts by weight of capsules and 70 parts of flexographic vehicle, to provide a printable ink which was applied to portions of a surface of sheets of paper by means of a gravure roll which printed the desired portion of the surface of the sheets of paper with the capsule coating. The coating dried on the paper promptly. When the resulting coated sheets were assembled with the coated portions facing adjacent sheets activated with attapulgite clay and writing pressure applied against the treated surface, a strong colored mark was produced.

Example X About 30 parts of capsules produced in accordance with Example I were mixed with 70 parts of a mixture of 6 parts of cellulose acetate and 64 parts of acetone. The resulting mixture was applied to one surface of sheets of paper by means of a doctor blade. The sheets were permitted to dry in the air. The surface of the sheets of paper coated with the capsules provided an excellent means of copying.

Example XI About 40 parts of paraflin wax having a melting point of 135 F. and 20 parts of FTC-200 petroleum wax (Fischer-Tropsch-l) were melted together at C. Into the resulting molten mixture were added about 5 parts of Alpex resin (a cyclized rubber resin) and 120 parts of Schenectady ST-5115 resin and the resulting clear melt reheated to 120 C. and maintained at this temperature. About parts of a solution of 5 parts of phenyl leuco auramine in 120 parts of butyl benzyl phthalate and 0.5 part of dimethylethanolamine, heated to 120 C. was added with rapid agitation to the foregoing melt in a Waring Blendor. The emulsion so formed was sprayed via a hot air stream C. temperature) inlet into a chilled atmosphere and the resulting spherical particles collected ranged in size from 1 to 60 microns. When subjected to writing pressures, these spheres ruptured and exuded the marking fluid which gave a strong blue coloration both on a paper sheet coated with attapulgite clay and on a paper sheet coated with citric acid.

12 As will be apparent from the foregoing examples various components of film-formers, plasticizers, marking fluids, dyes, pigments and binders may be employed. 5 Listed below in Table 2 are some of the components which may be employed.

TABLE 2 Binder Film Forming Resin or Polymer Plasticizer Resin Solvent or Fluid For Dye or Dye or Pigment Binder Solvent or Dispersion Medium Pigment Dispersion Medium Ce lulose acetate dibutyl-phthalate. acetone mineral oil oil soluble blue A carboxymethyl- Water.

(du Pont). cellulose. fiydr xyethylcellulose polylezhylene glywater rapeseed oil. carbon black nitrocellulose methanol.

co 00. Ze none water methanol mineral oil butyl ether of casein Wateralkali. crystal violet. yrenebutadiene copolymer do water chlorinated bimalachite green polyviuylchloride none.

phenyl. lactone. plastisol. Melamineformaldehyde do do amyl biphenyl phthalocyanine methylmethacryltoluene.

blue pigment. ate. Polyvillylchloride dioetyl adipate none polyethylene crystal violet nitrocellulose methanol glycol 400. carbiriol. toluene. y yl acetate-.. cottonseed il ultramarine blue lithovarnlsh none. yv pyrrolidone. amyluaphthalene. Hectograph hot melt resin"... D0.

White A du Pont. Petroleum resin paraffin wax none thirlidieti'hylerio methyl violet. starch water.

g yco Piccopale (Penna. Indus.

Chemical Co.) mineral oil Oyclized rubber do "Troi oir polyethylene Cadmium Red cellulose acetate-.- acetone- (Andersonglycol 400. Lithopone Eriehgrd Oil Dup Glidden.

orp. o yterpene resin. parafiin wax none glycerol pigment gelatin water. Piccolyte (Penn Chemc mineral oil Example XII An emulsion was prepared by homogenizing 100 parts of a 5050 mixture of polyethylene glycol 400 and ethoxytriglycol containing 7 parts of Spirit Hectograph Black A (a black pigment) (General Dyestutf Co.) into a molten mixture of 50 parts of parafiin wax and 45 parts of Piccopale 100 (a petroleum hydrocarbon resin). The resulting emulsion was sprayed into a chilled atmosphere and the solidified particles containing the colored fluid collected and stored. The spheres possessed a particle size of from 1 to 60 microns.

Example XIII About 50 parts of Geon 121 resin (polyvinyl chloride resin) was dispersed in 50 parts of dioctylphthalate as a plasticizer. Into this mixture was emulsified 50 parts of polyethylene glycol (mol. wt. 400) containing parts of carbon black. The resulting emulsion was sprayed into an air chamber at a temperature of 350 F. in order to fuse the resin and plasticizer about the fluid colored particles to form capsules containing marking fluid.

Example XIV About 50 parts of capsules prepared according to Example I were dispersed in 50 parts of Geon 121 resin and 50 parts of dioctylphthalate to provide a paste. The

resulting paste was printed onto paper and the coating cured by passing the coated paper over rollers at 350 F. An excellent copy sheet was produced.

It will be appreciated that if more than one copy is wanted it is possible to coat the capsules of the invention on at least a portion of one side of sheets of paper and, if necessary, a reactive coating on the other side, so that by placing a pile of such sheets one upon the other and pressing upon them with a pencil or subjecting them to the blow of a typewriter key, a suitable number of copies can be obtained depending upon the amount of pressure applied and the thickness of the paper.

The terms and expressions which have been employed are used as terms of description and not of limitation, and it is not intended, in the use of such terms and expressions, to exclude any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the invention claimed.

What is claimed is:

1. A process for producing a free-flowing powder of microscopic discrete rupturable capsules comprising liquid droplets encapsulated within an outer rupturable shell of film-forming material, said encapsulating outer shell being formed directly by evaporation forces on the solvent of a film-former solution of a non-ionizable water-soluble film-former which comprises the continuous phase of suspended minute particles of an emulsion, the discontinuous phase of which emulsion comprises the liquid droplets and between about 23% and 80% by weight of the capsules, which process comprises producing an emulsion of the liquid droplets in a film-former solution in which the latter forms the continuous phase and is substantially insoluble in the liquid droplets, suspending minute particles of said emulsion in a gaseous atmosphere, and then subjecting said suspended emulsion particles to evaporation forces to produce said microscopic discrete capsules in the form of a free-flowing powder.

2. A process defined by claim 1, wherein the drying is accomplished by spray evaporation.

3. A process as defined by claim 1, wherein the resulting capsules which are produced have a diameter of between about 0.1 and microns.

4. A process for producing a free-flowing powder of microscopic discrete rupturable capsulescomprising'marking fluid droplets encapsulated within an outer rupturable shell of film-forming material, said encapsulating outer shell being formed directly by evaporation forces on the solvent of a film-former solution of a non-ionizable watersoluble film-former which comprises the continuous phase of suspended minute particles of an emulsion, the discontinuous phase of which emulsion comprises the marking fluid droplets and between about 23% and 80% by weight of the capsules, which process comprises producing an emulsion of the marking fluid in a film-former solution in which the latter forms the continuous'phase and is substantially insoluble in, the marking fluid, suspending minute particles of said emulsion in a gaseous atmosphere, and then subjecting said suspended minute emulsion particles to evaporation forces to produce said microscopic discrete capsules in the form of a free-flowing powder.

5. A process as defined by claim 4 wherein said marking fluid comprises a colored material.

6. A process for producing a free-flowing powder of microscopic discrete rupturable capsules comprising liquid droplets encapsulated within an outer rupturable shell of film-forming material, said encapsulating outer shell being formed from a hot molten non-aqueous film-former comprising the continuous phase of an emulsion, the discontinuous phase of which emulsion comprises liquid droplets comprising between about 23% and 80% by weight of the emulsion, which process comprises producing an emulsion of the liquid droplets in said hot molten nonaqueous film-former in which the latter forms the continuous phase and is substantially insoluble in the liquid droplets, suspending minute particles of said emulsion in a gaseous atmosphere, and cooling the suspended particles to solidify said film-former and produce microscopic discrete rupturable capsules in the form of a free-flowing powder.

7. A process as defined by claim 6, wherein the resulting capsules have a diameter between about 0.1 and 70 microns.

8. A process for producing a free-flowing powder of microscopic discrete rupturable capsules comprising liquid droplets encapsulated within an outer rupturable shell of film-forming material, said encapsulating outer shell consisting of a hydrophobic water-insoluble material pro duced by the chemical condensation of the reactive constituents of the film-former dissolved in aqueous solution, said solution comprising the continuous phase of an emulsion, the discontinuous phase of which emulsion comprises liquid droplets comprising between about 23% and 80% by weight of the capsules, which process comprises producing an emulsion of the liquid droplets in said aqueous solution of film-former constituents, causing said film-former constituents to undergo Chemical condensation about the liquid droplets, and thereby produce said microscopic discrete rupturable capsules in the form of a free-flowing powder.

9. A process for producing a free-flowing powder of microscopic discrete rupturable capsules comprising liquid droplets encapsulated within an outer rupturable shell of film-forming material, said encapsulating outer shell being formed of a plastisol film-former comprising the continuous phase of an emulsion, the discontinuous phase of which emulsion comprises liquid droplets comprising be tween about 23% and 80% by weight of the capsules, which process comprises producing an emulsion of the liquid droplets in said plastisol film-former in which the latter forms the continuous phase and is substantially insoluble in the liquid droplets, heating minute particles of said emulsion to thereby produce said microscopic discrete rupturable capsules in the form of a free-flowing powder.

10. A process for producing a free-flowing powder of microscopic discrete rupturable capsules comprising liquid droplets encapsulated within an outer rupturable shell of film-forming material, said encapsulating outer shell being formed directly by evaporation forces on the organic solvent of a film-former solution of a hydrophobic waterinsoluble film-former in an organic solvent which comprises the continuous phase' of suspended minute particles of an emulsion, the discontinuous phase of which emulsion comprises the liquid droplets, and between about 23% and by weight of the capsules, which process comprises producing an emulsion of the liquid droplets in the film-former solution in which the latter forms the continuous phase andis substantially insoluble in the liquid droplets, suspending minute particles of said emulsion in a gaseous atmosphere, and then subjecting said suspended emulsion particles to evaporation forces to produce said microscopic discrete capsules in the form of a free-flowing powder.

11. A free-fl0wing powder of microscopic discrete rupturable capsules having a particle size of between about 0.1 and 70 microns diameter, said capsules comp-rising liquid droplets encapsulated within an outer shell rupturable under pressure, said liquid droplets being substantially insoluble in and incapable of dissolving said outer shell and comprising between about 23% and 80% by weight of said capsules, said outer shell having a thickness comprising from about one-tenth to one-third of the capsule diameter and comprising a material selected from the class consisting of a non-ionizable water-soluble filmformer and a hydrophobic water-insoluble film-former.

12. A substantially dry free-flowing powder as defined by claim 11 wherein the capsules have a particle size of between about 1 and 20 microns diameter.

13. A substantially dry free-flowing powder as defined by claim 11 wherein the capsules have a particle size of between about 1 and 5 microns diameter.

14. A free-flowing powder of microscopic discrete rupturable capsules as defined by claim 11 wherein the outer shell material is a non-ionizable water-soluble film-former comprising a cellulosic material.

15. A free-flowing powder of microscopic discrete rupturable capsules as defined by claim 14 wherein the liquid droplets comprise a marking fluid.

16. A free-flowing powder of microscopic discrete rupturable capsules as defined by claim 11 wherein the shell material is a hydrophobic water-insoluble film-former comprising a chemical condensation polymer.

17. A free-flowing powder of microscopic discrete rupturable capsules as defined by claim 16 wherein the liquid droplets comprise a marking fluid.

18. A free-flowing powder of microscopic discrete rupturable capsules as defined by claim 11 wherein the shell material is a hydrophobic water-insoluble film-former comprising a vinyl polymer.

19. A free-flowing powder of microscopic discrete rupturable capsules as defined by claim 18 wherein the liquid droplets comprise a marking fluid.

20. A free-flowing powder of microscopic discrete rupturable capsules as defined by claim 11 wherein the shell material comprises a fusible wax material.

21. A free-flowing powder of microscopic discrete rupturable capsules as defined by claim 20 wherein the liquid droplets comprise a marking fluid.

22. A free-flowing powder of microscopic discrete rupturable capsules as defined by claim 11 wherein the liquid droplets comprise a marking fluid.

23. A record copying sheet having on at least a portion of one side thereof a coating of a free-flowing powder of microscopic discrete capsules comprising a rupturable shell containing therein a marking fluid capable of being liberated when the shells of said discrete capsules are ruptured upon being subjected to an external printing or marking pressure, said microscopic discrete capsules being those defined by claim 11.

24. A record copying sheet having on at least a portion of one side thereof a coating of microscopic discrete capsules comprising a rupturable shell containing therein a marking fluid capable of being liberated when the shells of said discrete capsules are ruptured upon being subjected to external pressure, said capsules being held to said sheet by a binder which is of a different substance from that forming the rupturable shell of said capsules, said microscopic discrete capsules being those defined by claim 11.

25. Paper having coated on at least a portion of a surface thereof microscopic discrete capsules comprising a rupturable shell containing therein a marking fluid capable of being liberated when the shells of said discrete capsules are ruptured upon being subjected to external pressure, said capsules being held to said sheet by a binder which is of a different substance from that forming the rupturable shell of said capsules, said microscopic discrete capsules being those defined by claim 11.

26. Paper as defined by claim 25 wherein the marking fluid comprises a colored transfer substance.

' ing a color when in the presence of an acidic substance.

29. Paper as defined by claim 25 wherein the capsules have a diameter of between about 0.1 and 70 microns.

References Cited in the file of this patent UNITED STATES PATENTS 2,650,895 Wallenmeyer Sept, 1, 1953 2,711,375 Sandberg June 21, 1955 2,712,507 Green July 5, 1955 2,777,798 Hochberg Jan. 15, 1957 2,800,457 Green July 23, 1957 2,800,458 Green July 23, 1957 UNITED STATES PATENT OFFICE CERTIFICATE, OF CORRECTION Patent No,, 3 016 368 January 9 1962 Norman Macaulay It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 1 line 31 for ,"bands" read hands ---3 column 5 line 1O for "particles" read particle line 42,, for "'hydropholic" read hydrophobic column 'Z line 11, before "colored" insert a column 9 line 6 for "by" read of columns 11 and 12 TABLE 2"", the horizontal lines. beginning "Petroleum resin! and "Piccopale" should be presented as a single composition and not as two separate compositions as in the patent.

Signed and gsealed this 19th day of June 1962,

(SEAL) Attest ERNEST W. SWIDER v DAVID L. LADD Attesting Officer Commissioner of Patents UNITED STATES PATENT OFF-ICE CERTIFICATE, OF CORRECTION Patent Noe 3 O16 3O8 January 9 1962 NormanMacaulay It is hereby certified that error appears in the above numbered patant requiring correction and that the said Letters Patent should read as corrected below.

Column l line 31,, for -"bands" read hands column 5 line 10 for "particles" read particle line 42 for "hydropho1ic' read hydrophobic column '7 line 11,, before "coloned' insert a column 9 line 6 for "by" read of columns 11 and 12,, TABLE 2" the horizontal lines beginning "Petroleum resin"? and "Piccopale" should be presented as a single composition and not as two separate compositions as in the patent Signed and sea1ed this 19th day of June 1962.

(SEAL) Attest ERNEST w. SWIDER DAVID A D Attesting Officer Commissioner of Patents 

1. A PROCESS FOR PRODUCING A FREE-FLOWING POWDER OF MICROSCOPIC DISCRETE RUPTURABLE CAPSULES COMPRISING LIQUID DROPLETS ENCAPSULATED WITHIN AN OUTER RUPTURABLE SHELL OF FILM-FORMING MATERIAL, SAID ENCAPSULATING OUTER SHELL BEING FORMED DIRECTLY BY EVAPORATION FORCES IN THE SOLVENT OF A FILM-FORMER SOLUTION OF A NON-IONIZABLE WATER-SOLUBLE FILM-FORMER WHICH COMPRISES THE CONTINUOUS PHASE OF SUSPENDED MINUTE PARTICLES OF AN EMULSION, THE DISCONTINUOUS PHASE OF WHICH EMULSION COMPRISES THE LIQUID DROPLETS AND BETWEEN ABOUT 23% AND 80% BY WEIGHT OF THE CAPSULES, WHICH PROCESS COMPRISES PRODUCING AN EMULSION OF THE LIQUID DROPLETS IN A FILM-FORMER SOLUTION IN WHICH THE LATTER FORMS THE CONTINUOUS PHASE AND IS SUBSTANTIALLY IN- 